malcolmlewis wrote:

> What are the 'C States Control' and 'AC Recovery' settings in the BIOS?

This will get very specific for Dell, as names in BIOS are vender
specific. For me on the Optiplex 7010, "Deep Sleep" is disabled as it
powers off the NIC and thus breaks WOL while "Block Sleep" ist not allowed.
AC recovery is set to "off" as starting all PCs at once after a blackout
might trigger a fuse.
I did spent quit some time with these settings, and changing them will
not result in a proper shutdown IME.
This morning about half of the machines were powered off. So the mystery
remains why some installations work as others just reboot.